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Topic: Putting the half-hardies to bed (Read 2182 times)

"Half-hardy" is the term I use for any species that needs a winter dormancy (to whatever degree,) but will not survive a typical winter outside, with "normal" outdoor protection, in a given location. When you think about that for a moment you'll see that geography is the primary factor in determining what plants are half-hardy in any particular place.

For me, in north-central Indiana, trident maple definitely fits that description. Bald cypress is at the extreme northern edge of its native range here, so I treat it as half-hardy. Japanese black pine will survive our winters outdoors, but then struggles all thru the following growing season. So I treat it as half-hardy. Others that I don't presently have, but that are half-hardy here, include cedar of Lebanon, live oak, and crape myrtle.

I overwinter my half-hardies in an unheated, uninsulated "mudroom" at the back of our house. The room traps a bit of heat escaping from the house, as well as some solar radiation; and of course it stops wind. A "Windowbridge" (TM) mounted over a south-facing window provides two adjustable shelves. An inexpensive recording thermometer lets me track daily highs and lows.

A series of observations last winter established that the nite-time temperatures inside the mudroom are usually 10° F higher than the outside temps.

Yesterday I got the last of the room's winter residents prepped and inside. Besides half-hardies, I use the mudroom for one-season overwintering of anything that, for whatever reason, would be unusually susceptible to cold. That includes a yew cutting going into its first winter on its own roots, and a shohin yew that I repotted at the beginning of October. (Long story, and not my usual practice!) I also use it for new/young trees that are spending their first winter with me, especially if any that came from a milder climate.

And it's where I keep my serissas. Contrary to what most books say, I think serissa would be better considered subtropical, or even warm-temperate. There are others who agree with me, but that's a topic for another thread. I will give the serissas some extra care: whenever I can expect the temperature in the mudroom to fall below 20° F, I'll pull them into a milder spot for the duration.

There's a bit of shelf room left. I did let my wife know that I'd like a couple of young JRP's (Pinus densiflora) from Kaede Bonsai-en, for Christmas.

Thanks, Larry. In case anyone is interested, I bought the Windowbridge a number of years ago from Gardener's Supply. They may or may not still carry it.

Jerry, you read it right: just daylight thru a south-facing window. The serissas do lose some of their leaves, but not all, in my experience so far. This is only my 3d winter treating them as something other than tropical. I'm still figuring out how much cold they can take. I've learned they can handle temps into the upper 20's F without missing a beat; but I also learned, last year, that 13 F (7 C, approx) is too cold! The limit lies somewhere between those two.

Nathan, I don't allow foliage to touch the glass. Otherwise -- well, the trees are in there to be kept cold, just not too cold. If it were tropicals in there, it would be a different story. The air is colder in the inch or two next to the glass, and that could make a difference with a tropical tree.